214 Dr. Smith's Inquiry into the Structure of Seeds. 



very powerfully excite the vital principle of the budding vege- 

 table. In the few cases where one or more Cotyledons and a 

 distinct Albumen are together present, it does not seem neces- 

 sary that the gas should act through the former upon the Albu- 

 men, the two organs being but little connected, and its opera- 

 tion en the latter being independent of all vital or organic laws; 

 but either the gas itself, or the heat produced, may very well so 

 stimulate the vital principle of the Cotyledons, as to propel their 

 fluids into the Embryo and assist germination. This opinion is 

 the more probable, as those fluids must be supposed more truly 

 of the nature of sap, and more immediately fit for the use of 

 the infant plant, than the liquor of the Albumen. However this 

 may be, the existence of a Cotyledon or Cotyledons, together 

 with a separate Albumen, in seeds, seems to me so unusual, as 

 not to occasion much difficulty, and I would define a Cotyledon 

 to be a vital organ, capable, as such, of being stimulated by 

 oxygen, heat, or both, for the propulsion of its contents ; while such 

 an Albumen is merely a repository of nutritious vegetable mat- 

 ter, subject to the laws of chemistry alone, and only passively 

 resigning those contents to the absorbing powers of the Embryo, 

 to which it is attached. 



I must now, under the impression of what has just been ad- 

 vanced, return to the arrangement of plants by their Cotyledons. 



Plants in general are Dicotyledonous, having a pair of these 

 organs, which commonly rise out of the ground ; but if they do 

 not, it appears, from the consideration of the Leguminous tribe, 

 that such a difference could scarcely serve for a generic distinc- 

 tion, much less for that of a Class or Order. It also appears 

 that, if the number of Cotyledons exceeds two, as in Pinus and a 

 few other instances, the difference is of little or no use for sy- 

 stematical purposes, and of no physiological importance what- 

 ever. 



